JP2002349575A - Oil impregnated sintered bearing and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil impregnated sintered bearing capable of ensuring a low friction performance at the time of starting and reducing cost. SOLUTION: Raw material particulates obtained by formulating particulates of copper based metal 60, particulates of iron based metal 61 in which a copper component is less and an iron component is more than the copper based metal 60 and a particle diameter is large and tin 62 having a particle diameter being larger than that of the copper based metal 60 and being smaller than that of the iron based metal 61 are compression-molded in a metal mold to a particulate compression molded body and are sintered. A surface of the bearing 15, particularly a skin layer of an inner periphery surface 15a of the bearing contacted with a rotation shaft is formed by the copper based metal 60 and other parts of the bearing 15 are formed by the iron based metal 61.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bearing and a method of manufacturing the same, and more particularly to a so-called sintered oil-impregnated bearing which is sintered and impregnated with lubricating oil and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a so-called sintered oil-impregnated bearing having a self-lubricating effect by impregnating a porous material with a lubricating oil in order to reduce the number of times of lubricating oil replenishment is known as a bearing. . In this bearing, a bearing hole that supports the rotation shaft is formed, and the outer peripheral surface of the rotation shaft and the inner peripheral surface of the bearing hole are smoothly slid by the lubricating oil. The self-refueling effect is caused by being elicited.

However, in this sintered oil-impregnated bearing, when the load on the rotating shaft increases, the lubricating oil is pressed against the rotating shaft and pressed into the porous inner peripheral surface, and the gap between the rotating shaft and the inner peripheral surface is increased. There is a problem that the oil film is insufficient. In particular, when used as a bearing for the output shaft of a motor for a power window and when the output shaft is stationary with a load applied for a long period of time, the oil film between the rotating shaft and the bearing becomes insufficient, causing abnormalities at startup. Wear sometimes occurred. Conventionally, therefore, a bearing made of only a copper-based material having relatively low friction or a bearing made of a material obtained by adding a solid lubricant such as graphite or molybdenum sulfide (MoS ₂ ) to a copper-based material is used. Had been.

[0004]

However, copper-based materials and materials obtained by adding graphite, molybdenum sulfide, and the like thereto are expensive, and bearings made of copper-based materials are expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the invention is to provide a sintered oil-impregnated bearing and a sintered oil-impregnated bearing capable of ensuring low friction performance at the time of starting and reducing costs. It is to provide a manufacturing method.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 comprises a powder of a copper-based metal and a copper-based metal having a lower copper content and a higher iron content than the copper-based metal. The gist of the present invention is that a raw material powder composed of a powder blended with a powder of an iron-based metal having a large particle size is compression molded and sintered.

According to a second aspect of the present invention, there is provided a powder of a copper-based metal, a powder of an iron-based metal having a smaller copper content than the copper-based metal, a larger iron content, and a larger particle size; Raw material powder comprising a powder blended with a low melting temperature metal having a particle size larger than the metal particle size and smaller than the particle size of the iron-based metal, and having a melting point lower than the melting points of the copper-based metal and the iron-based metal The gist is that the body is compression molded and sintered.

According to a third aspect of the present invention, there is provided a powder mixture of a copper-based metal powder and a powder of an iron-based metal having a smaller copper content and a larger iron content and a larger particle diameter than the copper-based metal. The first raw material powder composed of the following is compression-molded into a part including the inner peripheral surface that comes into contact with the rotating shaft, and the second raw material powder composed of only the iron-based metal powder is formed.
The gist of the present invention is that the raw material powder is compression-molded into other parts, and the powder compression-molded bodies of both parts which are compression-molded integrally are sintered.

The invention described in claim 4 is the first to third aspects of the present invention.
In the sintered oil-impregnated bearing according to any one of the above, the gist is that the particle diameter of the iron-based metal is set to be five times or more the particle diameter of the copper-based metal.

[0010] The invention described in claim 5 provides the invention according to claims 1 to 4.
In the sintered oil-impregnated bearing according to any one of the above, the gist is that the particle diameter of the copper-based metal is 10 to 30 μm. The invention according to claim 6 is a powder of a copper-based metal constituting at least a part of an inner peripheral surface that is in contact with a rotating shaft, and an iron component constituting the other part and having a less copper component than the copper-based metal. A powder blending step of blending a powder of an iron-based metal having a large particle size into a raw material powder, and a molding step of filling the raw material powder in a mold and compression molding into a powder compression molded body When,
The gist of the present invention includes a sintering step of sintering the powder compression molded body, and a lubricating oil impregnation step of impregnating the sintered powder compression molded body with lubricating oil.

According to the first and second aspects of the present invention, the sintered oil-impregnated bearing comprises a copper-based metal powder and a copper-based metal having a smaller amount of a copper component than the copper-based metal and a large particle size of an iron component. A raw material powder composed of a powder blended with a large iron-based metal powder is compression-molded and sintered. Therefore, when the raw material powder is compression-molded, the copper-based metal particles having a small particle diameter pass through the gap between the iron-based metals having a large particle diameter, and the surface (surface layer) of the powder compression-molded body (that is, the sintered oil-impregnated bearing). More likely to appear. as a result,
The surface of the sintered oil-impregnated bearing, in particular, the inner peripheral surface portion in contact with the rotating shaft is formed of a copper-based metal, and the other portions are formed of an iron-based metal. Thereby, the rotating shaft and the inner peripheral surface portion of the sintered oil-impregnated bearing can be brought into contact with a low frictional force, thereby suppressing abnormal friction during startup. Further, since the other parts of the sintered oil-impregnated bearing are made of inexpensive iron-based metal, the sintered oil-impregnated bearing can be manufactured at low cost.

Further, according to the second aspect of the present invention,
The low melting temperature metal having a particle size larger than the particle size of the copper-based metal and smaller than the particle size of the iron-based metal is located between the copper-based metal layer and the iron-based metal layer by the compression molding, and the low melting temperature metal is sintered. The melting temperature metal is melted first, and the copper-based metal and the iron-based metal can be combined, and the inside of the sintered oil-impregnated bearing can be made porous.

According to the third aspect of the present invention, a part of the sintered oil-impregnated bearing including the inner peripheral surface so that the inner peripheral surface in contact with the rotating shaft is made of copper-based metal is made of powder of copper-based metal. Then, compression molding is performed using a first raw material powder composed of a powder mixture of an iron-based metal powder having a smaller copper content than the copper-based metal, a larger iron content, and a larger particle size. The other portions are compression-molded with the second raw material powder consisting of only iron-based metal powder.
The other parts of the sintered oil-impregnated bearing that are not in contact with the rotating shaft are formed of inexpensive iron-based metal, so that the manufacturing cost of the sintered oil-impregnated bearing can be reduced.

According to the invention described in claim 4, according to claim 1 of the present invention,
In addition to the effects of the inventions described in (1) to (3), when the raw material powder is compression-molded, the copper-based metal particles easily pass through the gaps between the iron-based metals, and the powder compression-molded body (that is, the sintered oil-impregnated bearing) ) On the surface (surface layer).

According to the invention described in claim 5, according to claim 1,
In addition to the effects of the inventions described in the above-mentioned items 4, the particle diameter of the copper-based metal is 1
When the particle diameter of the copper-based metal becomes 0 μm or less, it is possible to prevent the copper-based metal powder from flying easily, and when the particle diameter of the copper-based metal becomes 30 μm or more, it is possible to prevent the frictional force between the copper-based metal particles from increasing. As a result, handleability of the copper-based metal during manufacturing can be improved.

According to the sixth aspect of the present invention, there is provided a conventional oil-impregnated bearing in which the inner peripheral surface of the sintered oil-impregnated bearing which is in contact with the rotating shaft is formed of a copper-based metal and then the other portions are formed of an iron-based metal. Since the number of manufacturing steps can be reduced as compared with the manufacturing method, the manufacturing cost of the sintered oil-impregnated bearing can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a first embodiment of a sintered oil-impregnated bearing embodying the present invention will be described with respect to a case where the first embodiment is applied to a small motor with a reduction gear of a power window of an automobile. This will be described with reference to FIGS. FIG. 1 is a sectional view of a small motor with a reduction gear using the sintered oil-impregnated bearing of the present invention. FIG. 2 is a sectional view of the sintered oil-impregnated bearing of the present embodiment. FIG. 3 is a plan view of the sintered oil-impregnated bearing.

As shown in FIG. 1, a motor 13 is integrally mounted on a housing 12 of a small motor 11 with a speed reducer. The metal rotating shaft 14 of the motor 13
Is rotatably supported by a sintered oil-impregnated bearing (hereinafter simply referred to as a bearing) 15. The bearing 15 is non-rotatably fitted into a mounting hole 16 provided in the housing 12. A worm 17 is connected to the tip of the rotating shaft 14, and the worm 17 meshes with a worm wheel 18 rotatably supported by the housing 12. Therefore, when the motor 13 rotates, the worm wheel 18 rotates at a lower rotation speed than the motor 13.

As shown in FIG. 2 and FIG.
Is formed in a cylindrical shape, and has an inner hole (inner peripheral surface) 15a through which the rotary shaft 14 passes, an outer peripheral surface 15b into which the mounting hole 16 of the housing 12 is inserted, and a notch 15
c is provided with one end face (upper end face in FIG. 2) 15d and the other end face (lower end face in FIG. 2) 15e. Tapered portions 15f, 15g are provided at both open ends of the inner hole 15a in the upper and lower end surfaces 15d, 15e, respectively.

FIG. 4 is an explanatory sectional view of a main part showing an internal structure of the sintered oil-impregnated bearing. The bearing 15 includes a copper-based metal 60,
It is formed by compression molding and sintering a powder mixture of an iron-based metal 61 and tin 62 as a low melting temperature metal. The inner and outer peripheral surfaces 15a and 15b, upper and lower end surfaces 15d and 15e (only the other end surface 15e is shown in FIG. 4), and a tapered portion 15
The surface layer of the bearing 15 forming f, 15g (only the tapered portion 15g is shown in FIG. 4) is made of a copper-based metal 60. Further, the inside of the bearing 15 other than the surface layer as other portions is made of an iron-based metal 61 and tin 62.

The iron-based metal 61 has a lower copper content and a higher iron content than the copper-based metal 60. The diameter of the copper-based metal 60 particles (hereinafter, referred to as the particle size of the copper-based metal 60) is set to 10 to 30 μm, and the diameter of the iron-based metal 61 particles (hereinafter, referred to as the particle size of the iron-based metal 61) is The grain size of the copper-based metal 60 is set to 5 times or more. The diameter of the tin 62 particles (hereinafter referred to as tin 62
Is larger than the particle size of the copper-based metal 60 and smaller than the particle size of the iron-based metal 61.

Hereinafter, a method for manufacturing the bearing 15 of the present embodiment will be described with reference to the drawings. FIG. 5 is a flowchart illustrating a method for manufacturing the bearing 15. FIG. 6 is a cross-sectional view illustrating a step of forming the bearing 15.

As shown in FIG. 5, first, a powder preparation step S
11, the copper-based metal 60, the iron-based metal 61 and the tin 6
The raw material powder F is prepared by mixing the powders of No. 2 and No. 2. Next, in the molding step S12, the raw material powder F prepared in the powder mixing step S11 is filled in a mold 20 as shown in FIG. 6A, and is shown in FIG. 6B. Thus, the powder compression molded body 30 is compression molded. More specifically, the mold 20 includes a cylindrical die 21 and a through hole 2 of the die 21.
1a is provided with a lower punch 22 for inserting the same, and an upper punch 23. The axial length of the through hole 21 a of the die 21 is longer than the axial length of the bearing 15. The through hole 21 a is provided so that the inner diameter thereof is the same as the outer diameter of the bearing 15.

The lower punch 22 includes a large-diameter portion 22a having the same diameter as the inner diameter of the through hole 21a,
A small diameter portion 22b having the same diameter as the inner diameter (diameter of the inner hole 15a) and extending at one end of the large diameter portion 22a, and a tapered shape between the large diameter portion 22a and the small diameter portion 22b. It is composed of a step 22c. The step 22c
Are formed so that the taper angle thereof is the same as the taper angle of the tapered portion 15g of the bearing 15.

The upper punch 23 has a lower punch insertion hole 23a at the center and is formed in a cylindrical shape. The diameter of the lower punch insertion hole 23a is set to be the same as the outer diameter of the small diameter portion 22b (that is, the inner diameter of the inner hole 15a), and the outer diameter of the cylindrical portion of the upper punch 23 is the inner diameter of the through hole 21a (that is, the bearing). 15 outer diameter). A tapered projection 23b is provided at one end of the cylindrical portion of the upper punch 23, and a projection 23c is formed at a predetermined position of the tapered projection 23b. The tapered projection 23b is formed such that the taper angle is the same as the taper angle of the tapered portion 15f of the bearing 15, and the projection 23c is
Is formed in a size corresponding to the notch 15c.

As shown in FIG. 6A, the small diameter portion 22b of the lower punch 22 is
a, and the space K formed by slightly inserting the large diameter portion 22a into the through hole 21a is filled with the previously prepared raw material powder F in a predetermined amount. Thereafter, as shown in FIG. 6B, the upper punch 23 is inserted into the lower punch fitting hole 23a by the small diameter portion 22b.
The outer periphery presses the raw material powder F while being inserted into the through hole 21a. Thus, the powder compression molded body 30 having the same shape and dimensions as the bearing 15 is compression molded. The tapered portion 15f of the bearing 15 is formed by pressing the tapered convex portion 23b, and the tapered portion 15g is formed.
Is formed by pressing the step 22c. The notch 15c of the bearing 15 is provided with the protrusion 23c.
Is formed by pressing. The powder compression molded body 30 is taken out from the mold 20, and the molding step is completed.

Next, in a sintering step S13, the powder compact 30 is sintered by a known method. At this time, tin particles of the low melting temperature metal tin 62
And the particles of the iron-based metal 61 are melted before the copper-based metal 60 and the iron-based metal 61 are bonded, and the inside of the powder compression molded body 30 (that is, the bearing 15) becomes porous.

Thereafter, in the coining step S14,
The powder compression molded body 30 sintered in the previous step is coined by a known method. And finally, the lubricating oil impregnation step S
15, the porous powder compact 3
The bearing 15 is manufactured by impregnating the lubricating oil with O in a known manner.

The bearing 15 manufactured by the above manufacturing method has inner and outer peripheral surfaces 15a and 15b, upper and lower end surfaces 15a and 15b.
The surface layers at d and 15e and the tapered portions 15f and 15g are made of a copper-based metal 60, and the other portions other than the surface layers are made of an iron-based metal 61 and tin 62. Hereinafter, the mechanism by which different constituent materials are formed on the surface layer and other portions of the bearing 15 will be described.

In the present embodiment, the particle size of the iron-based metal 61 is set to be at least five times the particle size of the copper-based metal 60, and the particle size of the tin 62 is larger than the particle size of the copper-based metal 60. The diameter is set smaller than the particle diameter of the iron-based metal 61. Therefore, when the compounded powder of these metals (that is, the raw material powder F) is compressed in the compression molding step, the copper-based metal 60 having the smallest particle size becomes the surface (surface layer) of the powder compression molded body 30.
And the iron-based metal 61 having the smallest particle diameter enters the inside of the powder compression molded body 30. The copper-based metal 60
The tin 62, which is larger than the particle size of the iron-based metal 61 and smaller than the particle size of the iron-based metal 61, is positioned between the copper-based metal 60 layer and the iron-based metal 61 layer in the powder compact 30. Become. Further, since the particle diameter of the copper-based metal 60 is much smaller than the particle diameter of the iron-based metal 61, the copper-based metal 60 particles receive the pressing force at the time of compression molding and receive the iron-based metal 61. The powder compression molded body 30 passing through the gap between the particles
(That is, the surface of the bearing 15).
Next, the reason why the particle size of the iron-based metal 61 is set to be five times or more the particle size of the copper-based metal 60 will be described with reference to FIGS.

FIG. 7 shows three ferrous metals 6 in contact with each other.
It is explanatory drawing for calculating the relative particle diameter of the copper-type metal 60 particle | grains which can pass through the clearance gap between 1 particles. FIG. 8 is an explanatory diagram for calculating the relative particle size of the copper-based metal 60 particles that can pass through the gap between the four iron-based metal 61 particles that are in contact with each other. As shown in FIG. 7, when the radius of the iron-based metal 61 particles is R and the radius of the copper-based metal 60 particles is r1, cosα = R / (R + r1) due to a triangular functional relationship. Since the angle α is 30 °, √3 (R + r1)
= 2R, and when solved, R = 6.4r1. That is, in this case, the radius R of the iron-based metal 61 particles (or the particle diameter of the iron-based metal 61) is 6.4 times or more the radius r1 of the copper-based metal 60 particles (or the particle diameter of the copper-based metal 60). For example, the copper-based metal 60 particles can pass through the gap between the three iron-based metal 61 particles that are in contact with each other.

As shown in FIG. 8, the radius of the iron-based metal 61 particles is R, the radius of the copper-based metal 60 particles is r2, and the ferrous metal 61 adjacent to the center of the copper-based metal 60 particles is r2.
Assuming that the distance between the particle center and the connection line is h2, cos β
= R / (R + r2). Since the angle β is 45 °, R√2 = R + r2, and when solved, R = 2.4r
It becomes 2. That is, in this case, the radius R of the iron-based metal 61 particles (or the particle size of the iron-based metal 61) is 2.4 times or more the radius r2 of the copper-based metal 60 particles (or the particle size of the copper-based metal 60). For example, the copper-based metal 60 particles can pass through the gap between the four iron-based metal 61 particles that are in contact with each other.

When considering the particle space between the iron-based metals 61 in the above two cases together, the copper-based metal 60
Assuming that the average radius of the particles is r, R = r (6.4 + 2.
4) /2=4.4r. When this is converted to an integer in which the gap between the iron-based metal 61 particles becomes larger, that is, the copper-based metal 60 particle easily passes through the gap between the iron-based metal 61 particles,
R = 5r. That is, the radius R of the iron-based metal 61 particles
If (or the particle diameter of the iron-based metal 61) is at least 5 times the radius r (or the particle diameter of the copper-based metal 60) of the copper-based metal 60 particles, the copper-based metal 60 particles will It becomes easier to pass through the gap.

According to the bearing 15 and the method of manufacturing the same according to the present embodiment, the following effects can be obtained. (1) In the present embodiment, the surface of the bearing 15, in particular, the motor 1
The surface layer of the inner peripheral surface 15a of the bearing 15 which is in contact with the rotating shaft 14 is formed of a copper-based metal 60, and the other parts of the bearing 15 are formed of an iron-based metal 61. Therefore, the rotating shaft 14 and the inner peripheral portion of the bearing 15 can come into contact with a low frictional force, suppressing abnormal friction at the time of starting, and the other portions are made of the inexpensive iron-based metal 61. Can be manufactured at low cost.

(2) In the present embodiment, the ferrous metal 61
Is set to be at least five times the particle size of the copper-based metal 60. Therefore, when the prepared powder of the iron-based metal 61 and the copper-based metal 60 is compression-molded into the powder compression-molded body 30 by the mold 20, the copper-based metal 60 particles are powdered for the reason and mechanism described in detail above. It tends to appear on the surface (surface layer) of the compression molded body 30 (that is, the bearing 15). As a result, the surface of the bearing 15, in particular, the inner peripheral portion of the inner peripheral surface 15 a of the bearing 15 in contact with the rotating shaft 14 of the motor 13 is formed of the copper-based metal 60, and the other portions are formed of the iron-based metal 61. The number of manufacturing steps can be reduced as compared with the conventional manufacturing method of molding.

(3) In the present embodiment, the tin 62 as the low melting temperature metal is set to be larger than the particle size of the copper-based metal 60 and smaller than the particle size of the iron-based metal 61. Therefore,
The tin 62 is located between the copper-based metal 60 layer and the iron-based metal 61 layer in the powder compression molded body 30 formed by compression molding. As a result, when the powder compression molded body 30 is sintered and formed, the tin 62 particles dissolve before the copper-based metal 60 particles and the iron-based metal 61 particles, and the copper-based metal 60 and the iron-based metal 61 are dissolved. Can be combined with the powder compact 3
0 (that is, the bearing 15) is porous.

(4) In the present embodiment, the particle size of the copper-based metal 60 is set to 10 to 30 μm. Therefore, when the particle diameter of the copper-based metal 60 becomes 10 μm or less,
It is possible to prevent the powder from fluttering easily, and prevent the frictional force between the copper-based metal 60 particles from increasing when the particle size of the copper-based metal 60 is 30 μm or more. As a result, the handleability of the copper-based metal 60 during manufacturing can be improved.

(Second Embodiment) A second embodiment of a sintered oil-impregnated bearing embodying the present invention will be described below with reference to FIGS. Note that, in the present embodiment, the first
The same reference numerals are given to the same portions as those of the embodiment, and the detailed description thereof will be omitted.

FIG. 9 is a sectional view of the sintered oil-impregnated bearing of this embodiment. FIG. 10 is a plan view of the sintered oil-impregnated bearing. A bearing 35 as a sintered oil-impregnated bearing is formed in a substantially cylindrical shape, and has an inner hole 36 through which the rotary shaft 14 is inserted.
An outer peripheral surface 35a for fitting into the mounting hole 16 of the housing 12, one end surface (lower end surface in FIG. 9) 35b, and the other end surface (upper end surface in FIG. 9) 35c provided with the cutout 37 are provided. ing.

The inner hole 36 has a straight hole portion 36a for making contact with the rotary shaft 14, and a tapered inclined hole portion 3 expanding from one end of the straight hole portion 36a toward the other end surface 35c.
6b. The upper and lower end surfaces 35c, 35
b, tapered portions 35d and 35e are provided at the open ends of the oblique hole portion 36b and the straight hole portion 36a, respectively.

FIG. 11 is an explanatory sectional view of a main part showing an internal structure of a sintered oil-impregnated bearing. The bearing 35 is made of a copper-based metal 6.
0, a compound powder of iron-based metal 61 and tin 62 as a low melting temperature metal is formed by compression molding and sintering. The inner and outer peripheral surfaces on the side of the straight hole portion 36a, the lower end surface 35b, and the surface layer of the tapered portion 35e are made of a copper-based metal 60 (see FIG. 4). Further, the inside other than the surface layer as the other portion on the side of the straight hole portion 36a and the portion on the side of the oblique hole portion 36b are made of an iron-based metal 61. That is, FIG.
As shown in FIG. 1, the portion above the boundary between the straight hole portion 36a and the oblique hole portion 36b (the portion on the oblique hole portion 36b side) is entirely made of the iron-based metal 61.

The iron-based metal 61 has a lower copper content than the copper-based metal 60 and a higher iron content. The particle size of the copper-based metal 60 is 10 to 30 μm.
And the particle size of the iron-based metal 61 is
It is set to be at least 5 times the particle size of 0. The tin 62
Is larger than the particle diameter of the copper-based metal 60 and smaller than the particle diameter of the iron-based metal 61.

Hereinafter, a method of manufacturing the bearing 35 of the present embodiment will be described with reference to the drawings. FIG. 12 is a flowchart illustrating a method for manufacturing the bearing 15. 13 and 14 are cross-sectional views illustrating a step of forming the bearing 35.

As shown in FIG. 12, first, in the powder preparation step S21, a powder of only the iron-based metal 61 is prepared to prepare a second raw material powder F1, and the copper-based metal 60 and the iron-based metal F61 are prepared. The first raw material powder F is prepared by mixing powders of metal 61 and tin 62.
Prepare 2

Next, in a molding step S22, the raw material powder F1 prepared in the powder mixing step S21 is mixed with the raw material powder F1 shown in FIG.
As shown in FIG.
As shown in (b), the powder compression molded body 51 is compression molded. Thereafter, as shown in FIG. 14A, the raw material powder F2 prepared in the powder mixing step S21 is put into a mold 40.
Then, as shown in FIG. 14 (b), it is compression molded into a powder compression molded body 50 integral with the powder compression molded body 51.

More specifically, the mold 40 includes a cylindrical die 41, a lower punch 42 for inserting a through hole 41a of the die 41, a first upper punch 43 shown in FIG.
A second upper punch 44 is provided. The die 4
The axial length of one through hole 41 a is longer than the axial length of the bearing 35. The through hole 41a is provided such that the inner diameter thereof is the same as the outer diameter of the bearing 35.

The lower punch 42 has a large-diameter portion 42a having the same diameter as the inner diameter of the through hole 41a, and a small-diameter portion 42b.
And a step portion 42c formed in a tapered shape between the large diameter portion 42a and the small diameter portion 42b. The small diameter portion 42b has a cylindrical portion 42d having the same diameter as the straight hole portion 36a, and a truncated cone portion 4 corresponding to the oblique hole portion 36b.
2e. The step portion 42c is formed between the large diameter portion 42a and the truncated cone portion 42e, and is formed so that the taper angle thereof is the same as the taper angle of the taper portion 35d of the bearing 35. In addition, the step 42
A projection 45 is provided at a predetermined position of c. The protrusion 4
5 is formed in a size corresponding to the notch 37 of the bearing 35.

The first upper punch 43 is formed as shown in FIG.
As shown in (b), a lower punch insertion hole 43a is provided in the center, and is formed in a cylindrical shape. The lower punch insertion hole 4
3a is set to be the same as the outer diameter of the cylindrical portion 42d (that is, the inner diameter of the straight hole portion 36a), and the outer diameter of the cylindrical portion of the first upper punch 43 is set to the inner diameter of the through hole 41a (that is, the bearing 35). Outside diameter).

The second upper punch 44 is shown in FIG.
As shown in (b), a lower punch fitting hole 44a is provided in the center, and is formed in a cylindrical shape. The lower punch insertion hole 4
4a is set equal to the outer diameter of the cylindrical portion 42d (that is, the inner diameter of the straight hole portion 36a), and the outer diameter of the cylindrical portion of the second upper punch 44 is set to the inner diameter of the through hole 41a (that is, the bearing 35a). Outside diameter). Further, one end of the cylindrical portion of the second upper punch 44 has a tapered convex portion 44b.
Is provided. The tapered convex portion 44b is formed so that the taper angle thereof is equal to the taper angle of the tapered portion 35e of the bearing 35.

Then, as shown in FIG. 13A, the small diameter portion 42b of the lower punch 42 is
1a, and the large-diameter portion 42a is slightly inserted into the through hole 41a.
The previously prepared raw material powder F1 is filled in a predetermined amount.
Then, as shown in FIG. 13B, the first upper punch 43 is inserted into the lower punch fitting hole 43a by the small diameter portion 42.
The cylindrical portion 42d of b is inserted, and the outer periphery of the cylindrical portion presses the raw material powder F1 to some extent while being inserted into the through hole 41a. Thereby, the oblique hole 36b of the bearing 35
Powder compact 5 having the same shape and dimensions as the side part
1 is compression molded. Tapered portion 35d of the bearing 35
Is formed by pressing along the step 42c, and the notch 37 of the bearing 35 is formed by pressing along the protrusion 45.

Next, the first upper punch 43 is pulled out from the inside of the die 41, and as shown in FIG. 14A, the raw material previously prepared in the space K above the powder compression molded body 51. The powder F2 is filled in a predetermined amount. Then, FIG.
As shown in (b), the second upper punch 44 is inserted into the lower punch fitting insertion hole 44a in the cylindrical portion 42 of the small diameter portion 42b.
d is inserted, and the raw material powder F2 is strongly pressed while the outer periphery of the cylindrical portion is inserted into the through hole 41a. As a result, the powder compression molded body having the same shape and dimensions as the portion of the bearing 35 on the side of the straight hole portion 36a becomes the powder compression molded body 5
The powder compression molded body 50 is compression molded so as to be integrated with the powder compression molded body 50. The tapered portion 35e of the bearing 15 is formed by pressing the tapered convex portion 44b. Then, the powder compression molded body 50 is taken out from the mold 40, and the molding step is completed.

Next, in a sintering step S23, the powder compression molded body 50 is sintered by a known method. At this time, tin particles of the low melting temperature metal tin 62
And the iron-based metal 61 are dissolved before the copper-based metal 60 and the iron-based metal 61 are bonded together, and the powder compression-molded body 50 (that is, the bearing 35, particularly, the portion near the straight hole 36 a) is melted. The inside becomes porous.

Thereafter, in the coining step S24,
The powder compression molded body 50 sintered in the previous step is coined by a known method. And finally, the lubricating oil impregnation step S
25, the porous powder compact 5
The bearing 35 is manufactured by impregnating the lubricating oil with 0 in a known manner.

The bearing 35 manufactured by the above-described manufacturing method has inner and outer peripheral surfaces and a lower end surface 35 on the side of the straight hole portion 36a.
b and the surface layer of the tapered portion 35 e are made of a copper-based metal 60. Further, the inside other than the surface layer as the other portion on the side of the straight hole portion 36a and the portion on the side of the oblique hole portion 36b are made of an iron-based metal 61.

Therefore, in this embodiment, the following effects can be obtained in addition to the effects described in (1) to (4) of the above embodiment. (5) In the present embodiment, the bearing 35 that comes into contact with the rotating shaft 14
Only the portion on the side of the straight hole portion 36a was compression-sintered and formed with a compounded powder of a copper-based metal 60, an iron-based metal 61 and tin 62.
By forming the portion of the bearing 35 on the side of the oblique hole 36b that does not contact the rotating shaft 14 with the inexpensive iron-based metal 61, the manufacturing cost of the bearing 35 can be reduced.

The above embodiments may be modified as follows. In the above embodiments, the powder of the iron-based metal 61 may be, for example, a powder containing only iron particles. Further, a material other than iron may be contained.

In the second embodiment, the porous material may be formed so that the portion on the side of the oblique hole 36b made of the iron-based metal 61 can also be oil-impregnated. In the above embodiments, the tin 62 is used as the low melting metal, but the low melting metal other than the tin 62 may be used. Also, an iron-based metal 61 and a copper-based metal 60
Other metals may be added to the powder of tin and tin 62, or a solid lubricant such as graphite or molybdenum sulfide (MoS ₂ ) may be added.

In the above embodiments, the notch 15c,
Instead of providing 37, a convex portion may be provided. In the second embodiment, the portion on the side of the oblique hole 36b is compression-molded, and then the portion on the side of the straight hole 36a is compression-molded. However, the portion on the side of the straight hole 36a is compression-molded. Thereafter, the portion on the side of the oblique hole portion 36b may be compression molded.

In the above embodiments, the particle size of the iron-based metal 61 may be set to be 3 to 5 times the particle size of the copper-based metal 60. In each of the above embodiments, the oil-impregnated sintered bearing applied to a small motor with a reduction gear of a power window of an automobile has been embodied, but may be implemented in other oil-impregnated sintered bearings.

Next, technical ideas that can be grasped from the above embodiment and other examples will be described together with their effects. (1) a powder of a copper-based metal, a powder of an iron-based metal having a smaller copper content than the copper-based metal and a larger iron content and a larger particle size, A first raw material powder comprising a powder blended with a low melting temperature metal having a particle diameter smaller than the particle diameter of the base metal and having a melting point lower than the melting points of the copper-based metal and the iron-based metal, is brought into contact with the rotating shaft; Compression molding to a part including the inner peripheral surface to be formed, and compression molding of the second raw material powder consisting only of iron-based metal powder to the other part, and powder compression molding of both parts compression molded integrally A sintered oil-impregnated bearing characterized by sintering a body.

Accordingly, low friction performance at the time of starting the sintered oil-impregnated bearing can be ensured, and the cost can be reduced. (2) The sintered oil-impregnated bearing according to (1) or claim 2, 4 or 5, wherein the low melting temperature metal is tin.

[0062]

According to the present invention, low friction performance at the time of starting the sintered oil-impregnated bearing can be ensured, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a small motor with a reduction gear using a sintered oil-impregnated bearing of the present invention.

FIG. 2 is a cross-sectional view of the sintered oil-impregnated bearing of the first embodiment.

FIG. 3 is a plan view of the sintered oil-impregnated bearing in the embodiment.

FIG. 4 is an explanatory sectional view of a main part showing an internal structure of the sintered oil-impregnated bearing in the embodiment.

FIG. 5 is a flowchart illustrating a method for manufacturing the sintered oil-impregnated bearing in the embodiment.

FIG. 6 is an exemplary sectional view for explaining the molding step of the sintered oil-impregnated bearing according to the embodiment;

FIG. 7 is an explanatory diagram for calculating a relative particle size of copper-based metal particles that can pass through a gap between three iron-based metal particles that are in contact with each other.

FIG. 8 is an explanatory diagram for calculating a relative particle size of copper-based metal particles that can pass through a gap between four iron-based metal particles that are in contact with each other.

FIG. 9 is a sectional view of a sintered oil-impregnated bearing according to a second embodiment.

FIG. 10 is a plan view of the sintered oil-impregnated bearing in the embodiment.

FIG. 11 is an explanatory cross-sectional view of a main part showing an internal structure of the sintered oil-impregnated bearing in the embodiment.

FIG. 12 is a flowchart illustrating a method for manufacturing the sintered oil-impregnated bearing in the embodiment.

FIG. 13 is a sectional view for explaining the forming step of the sintered oil-impregnated bearing in the embodiment.

FIG. 14 is a sectional view for explaining the forming step of the sintered oil-impregnated bearing in the embodiment.

[Explanation of symbols]

14 ... rotating shaft, 15, 35 ... bearing as sintered oil-impregnated bearing, 20, 40 ... mold, 30, 50 ... powder compression molded body,
Reference numeral 60 denotes a copper-based metal, 61 denotes an iron-based metal, 62 denotes tin as a low melting point metal, F1 denotes a second raw material powder, and F2 denotes a first raw material powder.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 33/14 F16C 33/14 A (72) Inventor Takeshi Takeshi 390 Umeda, Kosai City, Shizuoka Prefecture Asmo Co., Ltd. (72) Inventor Teruo Shimizu 3-1-1 Koganecho, Niigata City, Niigata Prefecture Inside Mitsubishi Materials Niigata Works (72) Inventor Kousaku Fujita 3-1-1 Koganemachi, Niigata City, Niigata Prefecture F-term in Mitsubishi Materials Niigata Works (Reference) 3J011 AA10 AA20 BA02 DA01 DA02 KA02 LA01 QA01 SB03 SB19 4K018 AA05 AA24 BA02 BA13 BA20 BC12 FA47 HA04 JA03 KA03

Claims (6)

[Claims] 1. A raw material powder comprising a powder of a copper-based metal and a powder of an iron-based metal having a smaller copper content than the copper-based metal, a larger iron content, and a larger particle size, is compressed. A sintered oil-impregnated bearing characterized by being molded and sintered. 2. A powder of a copper-based metal, a powder of an iron-based metal having a smaller copper content than the copper-based metal and a larger iron content and a larger particle size, and a particle size larger than the copper-based metal and A raw material powder having a particle size smaller than the particle size of the iron-based metal and a powder mixed with a low melting temperature metal having a melting point lower than the melting points of the copper-based metal and the iron-based metal is compression-molded and sintered. A sintered oil-impregnated bearing characterized by being tied. 3. A first raw material powder comprising a powder mixture of a copper-based metal powder and a powder of an iron-based metal having a smaller copper content than the copper-based metal, a larger iron content and a larger particle size. Body
Compression molding is performed on a part including the inner peripheral surface that is in contact with the rotating shaft, and the second raw material powder composed of only iron-based metal powder is compression molded on the other part. A sintered oil-impregnated bearing obtained by sintering a powder compression molded body. 4. The sintered oil-impregnated bearing according to claim 1, wherein a particle size of the iron-based metal is set to be at least five times a particle size of the copper-based metal. . 5. The copper-based metal has a particle size of 10 to 30 μm.
The sintered oil-impregnated bearing according to any one of claims 1 to 4, wherein 6. A particle diameter of a copper-based metal powder constituting at least a part of an inner peripheral surface in contact with a rotating shaft, and a particle having another part and having a copper component less than the copper-based metal and an iron component. A powder blending step of blending a powder of an iron-based metal with a raw material powder having a large particle size; a molding step of filling the raw material powder in a mold and compression-molding the powder into a powder compression-molded body; A method for producing a sintered oil-impregnated bearing, comprising: a sintering step of sintering a green compact; and a lubricating oil impregnating step of impregnating the sintered powder compact with a lubricating oil.